| # UTC Time |
| |
| UTC time is the system’s best estimate of [Coordinated Universal Time][1]. |
| |
| [Architecture](architecture.md) covers the overall architecture of the time |
| synchronization system including the roles and responsibilities of each |
| component involved. |
| |
| On boards with a Real Time Clock (RTC), the system initializes UTC time from the |
| RTC shortly after power on. On all boards, the system periodically updates UTC |
| from one or more network time sources once a network is available. In principle, |
| these time sources could be configured separately for each product, but |
| currently all products source UTC from google.com using |
| [HTTPSdate](/src/sys/time/httpsdate_time_source/README.md). |
| |
| [Algorithms](algorithms.md) covers the time synchronization algorithms |
| implemented by the central component in the time synchronization system, |
| [Timekeeper](/src/sys/time/timekeeper). |
| |
| UTC is distributed to components using a |
| [kernel clock object](/docs/reference/kernel_objects/clock.md), with each |
| process holding a handle to this clock object (providing the parent process |
| supplied this clock). If you are developing components that use UTC, you should |
| read [UTC behavior](behavior.md) to learn how to acquire UTC time and understand |
| the behavior the UTC clock may exhibit both before and after time |
| synchronization. |
| |
| Previously the kernel maintained an additional internal UTC clock that could be |
| accessed through [`zx_clock_get`](/docs/reference/syscalls/clock_get.md). This |
| clock is deprecated and should no longer be used. |
| |
| [1]: https://en.wikipedia.org/wiki/Coordinated_Universal_Time |
